3-dimensional measuring device

ABSTRACT

A 3-dimensional measuring device includes: a light source unit; a projection optical system; a scanning mirror that is provided to be rotatable about a rotating shaft in a state of being inclined with respect to a shaft center of the rotating shaft to radiate a range-finding light within a plane crossing the rotating shaft in a rotary manner; a light-receiving optical system that receives a reflection range-finding light; a reference light optical system that is provided in a range outside a measuring range within a radiation range to receive and reflect the range-finding light as an internal reference light, the reference light optical system being capable of changing a light quantity of the internal reference light; and a light receiving element that receives the reflection range-finding light and the internal reference light.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of prior-filed U.S. patentapplication Ser. No. 16/106,309, filed Aug. 21, 2018, which is basedupon and claims benefit of priority from Japanese Patent Application No.2017-161303, filed Aug. 24, 2017, the entire contents of all of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a 3-dimensional measuring device thatradiates a range-finding light to a measurement target to measure adistance to the measurement target and detect a radiation direction ofthe range-finding light to thereby acquire 3-dimensional data on themeasurement target.

Generally, a 3-dimensional measuring device that acquires 3-dimensionaldata (3-dimensional point cloud data) of a number of points of ameasurement target is known. The 3-dimensional measuring device radiatespulsed laser beams to a measurement target as a range-finding light andreceives a reflection light of each pulsed laser beam reflected from themeasurement target. The 3-dimensional measuring device measures thedistance to the measurement target on the basis of the receivedreflection light and an internal reference light and detects a radiationdirection (a horizontal angle and a vertical angle) of the range-findinglight to thereby acquire 3-dimensional data on the measurement target.

For example, an internal reference light is acquired by splitting aportion of a range-finding light emitted from a light emitting elementusing a beam splitter or the like, for example. In this case, it isnecessary to perform a shutter switching operation of switching betweenan optical path for radiating a range-finding light to a measurementtarget and receiving a reflection light reflected from the measurementtarget using a light receiving element and an optical path for receivinga portion of the range-finding light split by a beam splitter or thelike, for example, using a light receiving element as an internalreference light. However, a conventional shutter having an electronicmechanism (an actuator, a DC brush motor, and the like) cannot easilyperform a high-speed switching operation due to its electricalcharacteristics and takes a considerable time in adjustment of its axis.

In contrast, Japanese Patent No. 4024912 discloses a laser range-findingdevice having a reference object disposed outside a monitored angularscanning range (a measuring region). In the laser range-finding devicedisclosed in Japanese Patent No. 4024912, a reference object is swept bya transmitted pulsed light. The transmitted pulsed light is reflected bythe reference object. In this case, the energy of the transmitted pulsedlight is attenuated by an attenuation filter provided in the referenceobject. In the laser range-finding device disclosed in Japanese PatentNo. 4024912, since the reference object reflecting the transmittedpulsed light swept by the transmitted pulsed light is disposed outside amonitored angular scanning range, a switching operation of a shutter isnot necessary.

However, in the laser range-finding device disclosed in Japanese PatentNo. 4024912, the degree of attenuation of the energy of the transmittedpulsed light changes continuously in a scanning direction. Due to this,in order to change the degree of attenuation of energy of thetransmitted pulsed light continuously, it is necessary to secure arelatively wide scanning range. However, in this case, there is aproblem that the monitored angular scanning range (the measuring region)narrows.

SUMMARY OF THE INVENTION

The present invention has been made to solve the above-describedproblems and an object thereof is to provide a 3-dimensional measuringdevice capable of eliminating a shutter's switching operation andsecuring a relative wide measuring range.

According to the present invention, the above problems are solved by a3-dimensional measuring device that radiates a range-finding light to ameasurement target, measures a distance to the measurement target on thebasis of an internal reference light and a reflection range-findinglight, which is the range-finding light reflected from the measurementtarget, and detects a radiation direction of the range-finding light tothereby acquire 3-dimensional data on the measurement target, the3-dimensional measuring device including: a light source unit that emitsthe range-finding light; a projection optical system that radiates therange-finding light emitted from the light source unit to arange-finding optical axis; a scanning mirror that is provided to berotatable about a rotating shaft in a state of being inclined withrespect to a shaft center of the rotating shaft to radiate therange-finding light guided from the projection optical system within aplane crossing the rotating shaft in a rotary manner; a light-receivingoptical system that receives the reflection range-finding light havingbeen reflected from the measurement target and guided by the scanningmirror; a reference light optical system that is provided in a rangeoutside a measuring range, in which the measurement target is irradiatedwith the range-finding light within a radiation range in which therange-finding light is radiated by the scanning mirror in a rotarymanner, to receive and reflect the range-finding light, reflected fromthe scanning mirror, as the internal reference light, this referencelight optical system being capable of changing a light quantity of thereflected internal reference light; and a light receiving element thatreceives the reflection range-finding light and the internal referencelight guided from the reference light optical system.

According to this configuration, the reference light optical system thatreceives the range-finding light reflected from the scanning mirror asthe internal reference light and reflects the internal reference lightis provided in a range outside the measuring range within the radiationrange of the range-finding light. The radiation range is a range inwhich the range-finding light is radiated to the scanning mirror in arotary manner. The measuring range is a range in which the range-findinglight is radiated to the measurement target. In this manner, since thereference light optical system is provided in a range outside themeasuring range within the radiation range, it is not necessary toprovide a shutter that switches between an optical path for radiatingthe range-finding light to the measurement target and receiving thereflection light reflected from the measurement target using the lightreceiving element and an optical path for receiving a portion of therange-finding light split by an optical member using the light receivingelement as the internal reference light. Due to this, it is possible toeliminate a shutter's switching operation.

Moreover, the reference light optical system can change the lightquantity of the reflected internal reference light. That is, the lightquantity of the internal reference light does not change depending on aradiation direction (a scanning direction) of the range-finding lightbut can be changed by the reference light optical system. Due to this,it is possible to acquire internal reference light having differentlight quantities using the reference light optical system whilesuppressing a radiation range (a scanning range) of the range-findinglight for acquiring the internal reference light. In this way, it ispossible to suppress the measuring range from narrowing and to secure arelatively wide measuring range.

Preferably, the reference light optical system includes a densityvariable filter capable of changing an optical density of a regionthrough which the internal reference light passes and a reflecting sheetof retroreflection that reflects the internal reference light havingpassed through the density variable filter.

According to this configuration, the reference light optical system hasa density variable filter. The density variable filter can change theoptical density of a region through which the internal reference lightpasses. Due to this, the transmittance of the internal reference lightwith respect to the density variable filter is variable. Due to this, itis possible to acquire internal reference lights having different lightquantities using the reference light optical system while suppressing aradiation range (a scanning range) of the range-finding light foracquiring the internal reference light. In this way, it is possible tosuppress the measuring range from narrowing and to secure a relativelywide measuring range. Moreover, the reference light optical system has areflecting sheet. The reflecting sheet causes retroreflection of theinternal reference light having passed through the density variablefilter. In this way, adjustment of an optical axis is not necessaryunlike a case in which a prism or a mirror reflects the internalreference light. Due to this, it is possible to eliminate the time andeffort taken in adjustment of an optical axis.

Preferably, the reference light optical system further includes a motorthat generates rotating force, and the density variable filter is adensity gradient filter which is provided to be rotatable with therotating force transmitted from the motor and in which the opticaldensity changes in a circumferential direction.

According to this configuration, the density variable filter is adensity gradient filter in which the optical density changes in thecircumferential direction. The density variable filter is provided to berotatable with the rotating force transmitted from the motor. Due tothis, when the density variable filter rotates, the optical density of aregion through which the internal reference light passes changes. Whenthe density variable filter in which a gradient of the optical densityis provided rotates, it is possible to acquire the internal referencelights having different light quantities while suppressing the radiationrange (the scanning range) of the range-finding light for acquiring theinternal reference light. In this way, it is possible to suppress themeasuring range from narrowing and to secure a relatively wide measuringrange.

Preferably, the reference light optical system includes a transmittancevariable filter capable of changing a transmittance of the internalreference light and a reflecting sheet of retroreflection that reflectsthe internal reference light having passed through the transmittancevariable filter.

According to this configuration, the reference light optical system hasa transmittance variable filter. The transmittance variable filter canchange the transmittance of the internal reference light. That is, thetransmittance of the internal reference light with respect to thetransmittance variable filter is variable. Due to this, it is possibleto acquire internal reference lights having different light quantitiesusing the reference light optical system while suppressing a radiationrange (a scanning range) of the range-finding light for acquiring theinternal reference light. In this way, it is possible to suppress themeasuring range from narrowing and to secure a relatively wide measuringrange. Moreover, the reference light optical system has a reflectingsheet. The reflecting sheet causes retroreflection of the internalreference light having passed through the density variable filter. Inthis way, adjustment of an optical axis is not necessary unlike a casein which a prism or a mirror reflects the internal reference light. Dueto this, it is possible to eliminate the time and effort taken inadjustment of an optical axis.

Preferably, the reference light optical system includes a motor thatgenerates rotating force and a reflectance gradient sheet which isprovided to be rotatable with the rotating force transmitted from themotor and in which a reflectance of the internal reference light changesin a circumferential direction.

According to this configuration, the reference light optical systemincludes the reflectance gradient sheet in which the reflectance of theinternal reference light changes in the circumferential direction. Thereflectance gradient sheet is provided to be rotatable with the rotatingforce transmitted from the motor. Due to this, when the reflectancegradient sheet rotates, the reflectance of the internal reference lightreflected from the reflectance gradient sheet changes. Due to this, itis possible to acquire the internal reference lights having differentlight quantities while suppressing the radiation range (the scanningrange) of the range-finding light for acquiring the internal referencelight. In this way, it is possible to suppress the measuring range fromnarrowing and to secure a relatively wide measuring range.

According to the present invention, it is possible to provide a3-dimensional measuring device capable of eliminating a shutter'sswitching operation and securing a relative wide measuring range.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a 3-dimensional measuring deviceaccording to an embodiment of the present invention;

FIG. 2 is a block diagram illustrating a control system of the3-dimensional measuring device according to the present embodiment;

FIG. 3 is a diagram illustrating a reference light optical system of thepresent embodiment;

FIG. 4 is a diagram illustrating a 3-dimensional measuring deviceaccording to a comparative example of the present embodiment;

FIG. 5 is a flowchart illustrating a distance calculation process of the3-dimensional measuring device according to the present embodiment;

FIG. 6 is a flowchart illustrating a distance calculation process of the3-dimensional measuring device according to the comparative example;

FIG. 7 is a diagram illustrating a first modification of the referencelight optical system of the present embodiment; and

FIG. 8 is a diagram illustrating a second modification of the referencelight optical system of the present embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, a preferred embodiment of the present invention will bedescribed in detail with reference to the drawings. The embodiment to bedescribed below is a preferred specific example of the presentinvention, and thus, the embodiment is accompanied by various preferabletechnical limitations. It is noted that the scope of the presentinvention is not limited to the embodiment unless the followingdescription explicitly limits the invention. In the drawings, similarconstituent elements will be denoted by the same reference numerals, andthe detailed description thereof will be omitted appropriately.

FIG. 1 is a block diagram illustrating a 3-dimensional measuring deviceaccording to an embodiment of the present invention. In the descriptionof the present embodiment, a case in which the 3-dimensional measuringdevice is a 3-dimensional laser scanner will be described.

As illustrated in FIG. 1 , a 3-dimensional measuring device 1 includes aleveling portion 2 attached to a tripod (not illustrated), a baseportion 3 provided on the leveling portion 2, a table portion 5 providedon the base portion 3 with a horizontal rotating portion 4 disposedtherebetween so as to be rotatable in a horizontal direction, and ascanning mirror 7 provided on the table portion 5 so as to be rotatablein a vertical direction (a height direction) about a vertical rotatingshaft 6.

The leveling portion 2 has three adjustment screws 8, for example.Leveling of the leveling portion 2 is performed when the adjustmentscrews 8 are adjusted so that an inclination sensor (not illustrated)provided in the table portion 5 detects a horizontal state.

The horizontal rotating portion 4 has a horizontal rotating shaft 11rotatably provided on the base portion 3 with a bearing 9 disposedtherebetween and supported vertically. The table portion 5 is supportedby the horizontal rotating shaft 11 and rotates integrally with thehorizontal rotating shaft 11.

A horizontal driving portion 13 including a horizontal driving motor 12and a horizontal angle detector (for example, an encoder) 14 thatdetects a rotation angle of the horizontal rotating shaft 11 areaccommodated in the horizontal rotating portion 4. The table portion 5rotates about the horizontal rotating shaft 11 with driving forcetransmitted from the horizontal driving motor 12. A rotation angle ofthe horizontal rotating shaft 11 in relation to the base portion 3 (thatis, a rotation angle of the table portion 5) is detected by thehorizontal angle detector 14.

A detection result (a horizontal angle) of the horizontal angle detector14 is input to the control operation unit 15. Driving of the horizontaldriving motor 12 is controlled by the control operation unit 15 on thebasis of the detection result of the horizontal angle detector 14.

A concave portion 16 is formed in a central portion of the table portion5. A first chamber 5 a and a second chamber 5 b are formed on both sidesof the concave portion 16. A vertical driving portion 17 and a verticalangle detector 18 are accommodated in the first chamber 5 a (the chamberon the left side in FIG. 1 ). A range-finding light emitter 19, a commonoptical path 21, a range finding unit 22, an imaging unit 23, and areference light optical system 24 are accommodated in the second chamber5 b (the chamber on the right side in FIG. 1 ). The control operationunit 15 is accommodated at a predetermined position inside the tableportion 5. Moreover, a display unit 25 and an operating unit 26 areprovided in a predetermined portion of the table portion 5.

The vertical rotating shaft 6 has a shaft center extending horizontallyand is rotatably supported on the table portion 5 with a bearing 27disposed therebetween. One end of the vertical rotating shaft 6protrudes toward the concave portion 16. The scanning mirror 7 isprovided in one end of the vertical rotating shaft 6 protruding towardthe concave portion 16 and is inclined at an angle of 45° with respectto the shaft center of the vertical rotating shaft 6. The scanningmirror 7 is supported inside the concave portion 16 by the verticalrotating shaft 6 and can rotate in a vertical direction about thevertical rotating shaft 6.

The vertical driving portion 17 has a vertical driving motor 28 thatrotates the vertical rotating shaft 6. The scanning mirror 7 rotateswith driving force transmitted from the vertical driving motor 28 viathe vertical rotating shaft 6. The scanning unit 29 of the presentembodiment has the vertical rotating shaft 6, the scanning mirror 7, andthe vertical driving motor 28.

A vertical angle detector 18 (for example, an incremental encoder) isprovided at the other end of the vertical rotating shaft 6. The rotationangle of the vertical rotating shaft 6 in relation to the table portion5 is detected by the vertical angle detector 18. The detection result (avertical angle) of the vertical angle detector 18 is input to thecontrol operation unit 15. Driving of the vertical driving motor 28 iscontrolled by the control operation unit 15 on the basis of a detectionresult of the vertical angle detector 18.

The range-finding light emitter 19 has a range-finding light source unit31 and a projection optical system 33 including an objective lens andthe like. The range-finding light source unit 31 is a semiconductorlaser or the like, for example, and emits a range-finding light 35 to arange-finding optical axis 32. The range-finding light 35 of the presentembodiment is an infrared pulsed laser beam as an invisible light. Therange-finding light source unit 31 is controlled by the controloperation unit 15 and emits a pulsed light in a predetermined stateincluding a predetermined light intensity, a predetermined pulseinterval, and the like.

The common optical path 21 has a first beam splitter 38 and a secondbeam splitter 39. The range finding unit 22 has a light-receivingoptical system 41 including a condensing lens and the like and a lightreceiving element 42. The light receiving element 42 receives areflection range-finding light 37 which is the range-finding light 35reflected from a measurement target (not illustrated) and which haspassed through the light-receiving optical system 41 and converts thereflection range-finding light 37 to an electrical signal. Moreover, thelight receiving element 42 receives an internal reference light 36guided from the reference light optical system 24 and converts theinternal reference light 36 to an electrical signal.

That is, the range-finding light 35 output from the range-finding lightsource unit 31 is guided to the common optical path 21 via theprojection optical system 33. The range-finding light 35 guided to thecommon optical path 21 is sequentially reflected from the first beamsplitter 38 and the second beam splitter 39 and is then guided to thescanning mirror 7. The range-finding light 35 having passed through thefirst beam splitter 38 and the second beam splitter 39 is absorbed by areflection preventing member (not illustrated).

The scanning mirror 7 is a deflection optical member and reflects therange-finding light 35 incident from a horizontal direction at a rightangle. Moreover, the scanning mirror 7 reflects the reflectionrange-finding light 37 and the internal reference light 36 incident onthe scanning mirror 7 toward the second beam splitter 39 in a horizontaldirection.

The range-finding light 35 guided from the common optical path 21 towardthe scanning mirror 7 is reflected from the scanning mirror 7 and isradiated to the measurement target. Moreover, the range-finding light 35guided from the common optical path 21 toward the scanning mirror 7 isreflected from the scanning mirror 7 and is radiated to the referencelight optical system 24 as the internal reference light 36. That is, ina measuring range within a radiation range of the range-finding light35, the range-finding light 35 is reflected from the scanning mirror 7and is radiated to the measurement target. On the other hand, in a rangeoutside the measuring range within the radiation range of therange-finding light 35, the range-finding light 35 is reflected from thescanning mirror 7 and is received and reflected by the reference lightoptical system 24 as the internal reference light 36. That is, thereference light optical system 24 is provided in a range outside themeasuring range within the radiation range of the range-finding light35. The internal reference light 36 is light which is a portion of therange-finding light 35 and is light received by the reference lightoptical system 24. The “radiation range” in the present application is arange in which the range-finding light 35 is radiated by the scanningmirror 7 in a rotary manner. Moreover, the “measuring range” is a rangein which the range-finding light 35 is radiated to the measurementtarget.

When the scanning mirror 7 rotates about the vertical rotating shaft 6,the range-finding light 35 is radiated in a plane (a vertical plane inthe present embodiment) crossing the vertical rotating shaft 6 in arotary manner. Moreover, when the table portion 5 is rotated by thehorizontal rotating portion 4 in a horizontal direction, therange-finding light 35 is radiated in a rotary manner in a horizontaldirection about the horizontal rotating shaft 11. Therefore, bycooperation of the rotation in the vertical direction of the scanningmirror 7 and rotation in the horizontal direction of the table portion5, the 3-dimensional measuring device 1 can scan the entire measuringrange with the range-finding light 35.

The reflection range-finding light 37 reflected from the measurementtarget present in the measuring range is incident on the scanning mirror7. The reflection range-finding light 37 incident on the scanning mirror7 is reflected from the scanning mirror 7 and is incident on the commonoptical path 21. The reflection range-finding light 37 passes throughthe second beam splitter 39 and is guided to the range finding unit 22.Moreover, the internal reference light 36 reflected from the referencelight optical system 24 provided in a range outside the measuring rangeis incident on the scanning mirror 7. The internal reference light 36incident on the scanning mirror 7 is reflected from the scanning mirror7 and is incident on the common optical path 21. The internal referencelight 36 passes through the second beam splitter 39 and is guided to therange finding unit 22.

The light receiving element 42 of the range finding unit 22 receives,via the light-receiving optical system 41, the reflection range-findinglight 37 reflected from the measurement target and the internalreference light 36 reflected from the reference light optical system 24.In the light receiving element 42, the reflection range-finding light 37and the internal reference light 36 are converted to an electricalsignal of the reflection range-finding light and an electrical signal ofthe internal reference light, respectively, and are transmitted to thecontrol operation unit 15. The distance to the measurement target ismeasured on the basis of a difference in time interval between thereflection range-finding light electrical signal and the electricalsignal of the internal reference light.

The control operation unit 15 calculates a coordinate value of themeasurement target on the basis of the measured distance to themeasurement target, the vertical angle detected by the vertical angledetector 18, and the horizontal angle detected by the horizontal angledetector 14. Moreover, the control operation unit 15 can obtain pointcloud data on the entire measuring range or point cloud data on themeasurement target by recording the coordinate value of the measurementtarget for respective pulsed lights. An angle detecting unit thatdetects the direction of the range-finding optical axis 32 includes thehorizontal angle detector 14 and the vertical angle detector 18. Thatis, the radiation direction of the range-finding light 35 is detected bythe angle detecting unit including the horizontal angle detector 14 andthe vertical angle detector 18.

The imaging element 45 is provided on an imaging optical axis of theimaging unit 23. The imaging element 45 has a pixel assembly and outputsa digital image signal. Examples of the imaging element 45 include a CCDor CMOS sensor, for example. The positions in the imaging element 45, ofthe respective pixels of the imaging element 45 can be specified.

FIG. 2 is a block diagram illustrating a control system of the3-dimensional measuring device according to the present embodiment. Theoperating unit 26, the vertical angle detector 18, and the horizontalangle detector 14 are electrically connected to the control operationunit 15. Angle detection signals output respectively from the verticalangle detector 18 and the horizontal angle detector 14 are input to thecontrol operation unit 15 and an operation signal output from theoperating unit 26 on the basis of an operator's operation is also inputto the control operation unit 15.

An operator operates the operating unit 26 to set conditions necessaryfor starting the measurement of the 3-dimensional measuring device 1.Examples of the necessary conditions include a measuring range, a pointcloud data density (pitch), and imaging conditions. The set conditionsand the like input by the operating unit 26 are displayed on the displayunit 25. In this way, an operator can ascertain the set conditions andthe like input by the operating unit 26 on the display unit 25. Theoperating unit 26 and the display unit 25 may be provided in the tableportion 5 and may be provided independently from the table portion 5 andmay be remote-controlled by a signal transmission medium such as radiowaves or infrared rays.

The control operation unit 15 drives the range-finding light source unit31, the horizontal driving motor 12, and the vertical driving motor 28and controls the display unit 25 that displays an operation state, ameasurement result, and the like. Moreover, an external storage device46 such as a memory card or a HDD is provided in the control operationunit 15. The external storage device 46 may be fixedly provided in thecontrol operation unit 15 and may be detachably provided.

The control operation unit 15 includes a computing unit 47 representedby a CPU, a storage unit 48, a range-finding light-emitting driving unit49 that controls light emission of the range-finding light source unit31, the horizontal driving portion 13 that drives and controls thehorizontal driving motor 12, and the vertical driving portion 17 thatdrives and controls the vertical driving motor 28. Moreover, the controloperation unit 15 includes a distance data processing unit 51 thatprocesses distance data obtained by the range finding unit 22 and animage data processing unit 52 that processes image data obtained by theimaging unit 23.

The storage unit 48 stores programs such as a sequence program forexecuting range-finding, measurement of a vertical angle, andmeasurement of a horizontal angle, a computation program for performingcomputation of range-finding, a measurement data processing program forexecuting processing of measurement data, an imaging program forcontrolling an imaging state of the imaging unit 23, an image processingprogram for executing image processing, and an image display program forcausing the display unit 25 to display data or a program or the like formanaging these programs in an integrated manner. Moreover, the storageunit 48 stores data such as measurement data and image data.

The computing unit 47 may have the function of the distance dataprocessing unit 51 and the function of the image data processing unit52. In this case, the distance data processing unit 51 and the imagedata processing unit 52 may not necessarily be provided.

The distance data processing unit 51 and the image data processing unit52 may be provided separately from the control operation unit 15. Forexample, another PC other than the control operation unit 15 may executethe functions of the distance data processing unit 51 and the image dataprocessing unit 52. In this case, for example, distance data and imagedata are transmitted from the 3-dimensional measuring device 1 to a PCvia communication means provided in the 3-dimensional measuring device 1and the PC. The PC executes distance data processing and image dataprocessing. Example of the communication means include opticalcommunication, radio communication, LAN, and the like.

FIG. 3 is a diagram illustrating the reference light optical systemaccording to the present embodiment. FIG. 4 is a diagram illustrating a3-dimensional measuring device according to a comparative example of thepresent embodiment. The imaging unit 23 is omitted in FIG. 3 for thesake of convenience. The same is true in FIGS. 7 and 8 .

First, a 3-dimensional measuring device 1A according to a comparativeexample of the present embodiment will be described with reference toFIG. 4 . In the 3-dimensional measuring device 1A according to thiscomparative example illustrated in FIG. 4 , a third beam splitter 55 anda first shutter 53 are provided between the projection optical system 33and the first beam splitter 38. The third beam splitter 55 and the firstshutter 53 are arranged in that order from the projection optical system33 toward the first beam splitter 38.

A fourth beam splitter 56 is provided between the light-receivingoptical system 41 and the light receiving element 42. Furthermore, asecond shutter 54, a density gradient filter 243, and a lens 57 areprovided between the third beam splitter 55 and the fourth beam splitter56. The second shutter 54, the density gradient filter 243, and the lens57 are arranged in that order from the third beam splitter 55 toward thefourth beam splitter 56.

The first and second shutters 53 and 54 each can adjust transmittance oflight. That is, the first and second shutters 53 and 54 each cantransmit light by opening the shutter and block light by closing theshutter. When the first shutter 53 is open, the range-finding light 35output from the range-finding light source unit 31 passes through thethird beam splitter 55 and the first shutter 53 and is reflectedsequentially from the first beam splitter 38 and the second beamsplitter 39 and is guided to the scanning mirror 7.

On the other hand, when the second shutter 54 is open, a portion of therange-finding light 35 output from the range-finding light source unit31 is reflected from the third beam splitter 55 and passes through thesecond shutter 54 as the internal reference light 36. The internalreference light 36 which has been reflected from the third beam splitter55 and has passed through the second shutter 54 passes through thedensity gradient filter 243 and the lens 57 and is guided toward thefourth beam splitter 56. The internal reference light 36 guided to thefourth beam splitter 56 is reflected from the fourth beam splitter 56and is received by the light receiving element 42.

The density gradient filter 243 is supported by a shaft 242 of the motor241 and is provided rotatable about the shaft 242 of the motor 241 withthe rotating force transmitted from the motor 241. An optical density ofthe density gradient filter 243 changes in a circumferential direction.Due to this, when the density gradient filter 243 rotates, an opticaldensity of a region in which the internal reference light 36 passesthrough the density gradient filter 243 changes. In this way, internalreference lights 36 having different light quantities are guided to thefourth beam splitter 56. The other constituent elements are similar tothe constituent elements of the 3-dimensional measuring device 1described in FIG. 1 .

In this manner, the 3-dimensional measuring device 1A according to thiscomparative example splits a portion of the range-finding light 35emitted from the range-finding light source unit 31 using the third beamsplitter 55 and controls opening/closing of the first and secondshutters 53 and 54. In this way, the internal reference light 36 isacquired. The details of the opening/closing control of the first andsecond shutters 53 and 54 will be described later. In the 3-dimensionalmeasuring device 1A according to this comparative example, since therange-finding light 35 and the internal reference light 36 cannot beprocessed simultaneously, a switching operation of the first and secondshutters 53 and 54 is necessary. Moreover, when the distance between the3-dimensional measuring device 1A and the measurement target is short,it is not possible to split the range-finding light 35 and the internalreference light 36 unless a switching operation of the first and secondshutters 53 and 54 is performed. However, in the 3-dimensional measuringdevice 1A according to this comparative example, it is difficult toperform a shutter switching operation at a high speed and it takes aconsiderable time in adjustment of an optical axis.

In contrast, in the 3-dimensional measuring device 1 according to thepresent embodiment, as illustrated in FIGS. 1 and 3 , the referencelight optical system 24 is provided in a range outside the measuringrange within the radiation range of the range-finding light 35 andreceives the range-finding light 35, reflected from the scanning mirror7, as the internal reference light 36 and reflects the same. Moreover,the reference light optical system 24 can change the quantity of thereflected internal reference light 36.

Specifically, the reference light optical system 24 includes a motor241, a density gradient filter 243, a reflecting sheet 244, and a filter245. The motor 241 has a shaft 242 and generates rotating force. Thedensity gradient filter 243 is supported by the shaft 242 of the motor241 and is provided to be rotatable about the shaft 242 of the motor 241with the rotating force transmitted from the motor 241. An opticaldensity of the density gradient filter 243 changes in a circumferentialdirection. In other words, a density gradient in which the opticaldensity changes in the circumferential direction is provided in thedensity gradient filter 243. The optical density of the density gradientfilter 243 may not necessary increase or decrease gradually in thecircumferential direction but may change in the circumferentialdirection. When the density gradient filter 243 rotates with therotating force transmitted from the motor 241, the optical density of aregion in which the internal reference light 36 passes through thedensity gradient filter 243 changes. Due to this, the transmittance ofthe internal reference light 36 with respect to the density gradientfilter 243 is variable. The density gradient filter 243 of the presentembodiment is one example of a density variable filter 246 (see FIG. 7 )capable of changing the optical density of the region through which theinternal reference light 36 passes.

The reflecting sheet 244 is provided on the opposite side of thescanning mirror 7 when seen from the density gradient filter 243 andreflects the range-finding light 35 having passed through the densitygradient filter 243. In this case, the reflecting sheet 244 causesretroreflection of the internal reference light 36. In this way,adjustment of an optical axis is not necessary unlike a case in which aprism or a mirror reflects the internal reference light 36. Due to this,it is possible to eliminate the time and effort taken in adjustment ofan optical axis.

The filter 245 is provided between the scanning mirror 7 and the densitygradient filter 243 and is formed of glass or the like, for example. Thefilter 245 can adjust a variation in a light quantity of the internalreference light 36 resulting from a fluctuation of the 3-dimensionalmeasuring device 1. Moreover, the filter 245 can suppress the internalreference light 36 from reflecting from the surface of the densitygradient filter 243. The filter 245 may not necessarily be provided.

The range-finding light 35 which has been reflected from the scanningmirror 7 and has passed through the filter 245 and the density gradientfilter 243 is reflected from the reflecting sheet 244. The internalreference light 36 reflected from the reflecting sheet 244 passesthrough the density gradient filter 243 and the filter 245 and isreflected from the scanning mirror 7. When the internal reference light36 passes through the density gradient filter 243, the optical densityof a region in which the internal reference light 36 passes through thedensity gradient filter 243 changes. That is, when the internalreference light 36 passes through the density gradient filter 243, thetransmittance of the internal reference light 36 with respect to thedensity gradient filter 243 changes. In this way, internal referencelights 36 having different light quantities are guided to and acquiredby the scanning mirror 7. The internal reference light 36 reflected fromthe scanning mirror 7 passes through the second beam splitter 39 and isguided to the light receiving element 42.

According to the 3-dimensional measuring device 1 according to thepresent embodiment, the reference light optical system 24 is provided ina range outside the measuring range within the radiation range. Due tothis, it is not necessary to provide a shutter (for example, the firstand second shutters 53 and 54) that switches between an optical path forradiating the range-finding light 35 to the measurement target andreceiving the reflection range-finding light 37 reflected from themeasurement target using the light receiving element 42 and an opticalpath for receiving a portion of the range-finding light 35 split by anoptical member (for example, the third beam splitter 55) using the lightreceiving element 42 as the internal reference light 36. In this way, itis possible to eliminate a shutter's switching operation.

Moreover, the reference light optical system 24 can changes the lightquantity of the reflected internal reference light 36. That is, thelight quantity of the internal reference light 36 does not changedepending on the radiation direction (a scanning direction) of therange-finding light 35 but can be changed by the reference light opticalsystem 24. Due to this, it is possible to acquire internal referencelights 36 having different light quantities using the reference lightoptical system 24 while suppressing a radiation range (a scanning range)of the range-finding light 35 for acquiring the internal reference light36. In this way, it is possible to suppress the measuring range fromnarrowing and to secure a relatively wide measuring range.

Specifically, as described above, the optical density of the densitygradient filter 243 changes in the circumferential direction. When thedensity gradient filter 243 rotates with the rotating force transmittedfrom the motor 241, the optical density of the region in which theinternal reference light 36 passes through the density gradient filter243 changes. Due to this, the transmittance of the internal referencelight 36 with respect to the density gradient filter 243 is variable.When the density gradient filter 243 in which a gradient of the opticaldensity is provided rotates, it is possible to acquire the internalreference lights 36 having different light quantities while suppressingthe radiation range (the scanning range) of the range-finding light 35for acquiring the internal reference light 36. In this way, it ispossible to suppress the measuring range from narrowing and to secure arelatively wide measuring range.

Next, a process of calculating (measuring) the distance to themeasurement target will be described with reference to the drawings.FIG. 5 is a flowchart illustrating a distance calculation process of the3-dimensional measuring device according to the present embodiment. FIG.6 is a flowchart illustrating a distance calculation process of the3-dimensional measuring device according to this comparative example.

First, a distance calculation process of the 3-dimensional measuringdevice 1A according to this comparative example will be described withreference to FIG. 6 . The configuration of main components of the3-dimensional measuring device 1A according to this comparative exampleis the same as that described with reference to FIG. 4 .

First, in step S21, the control operation unit 15 executes control sothat the first shutter 53 is closed and the second shutter 54 is open.In this way, the range-finding light 35 having passed through the thirdbeam splitter 55 is blocked by the first shutter 53. On the other hand,the range-finding light 35 having been reflected from the third beamsplitter 55 passes through the second shutter 54, the density gradientfilter 243, and the lens 57 as the internal reference light 36 and isreflected from the fourth beam splitter 56 and is guided to the lightreceiving element 42.

Subsequently, in step S22, the distance data processing unit 51calculates an internal light distance on the basis of the internalreference light (an internal light) 36 received by the light receivingelement 42. That is, the distance data processing unit 51 processesinternal light distance data on the basis of the internal referencelight 36 received by the light receiving element 42 and converted to anelectrical signal of the internal reference light. Subsequently, in stepS23, the storage unit 48 stores the intrinsic optical distance data.

Subsequently, in step S24, the control operation unit 15 executescontrol so that the first shutter 53 is open and the second shutter 54is closed. In this way, the range-finding light 35 having passed throughthe third beam splitter 55 passes through the first shutter 53 and issequentially reflected from the first beam splitter 38 and the secondbeam splitter 39 and is guided to the scanning mirror 7. Therange-finding light 35 is reflected from the scanning mirror 7 and isradiated to the measurement target. On the other hand, the range-findinglight 35 reflected from the third beam splitter 55 is blocked by thesecond shutter 54 as the internal reference light 36.

The processing order of step S24 may not necessarily be later than stepS23. For example, the process of step S24 may be executed between stepsS21 and S22 or between steps S22 and S23. A shutter response time(including a stabilization time) of each of the first and secondshutters 53 and 54 is approximately 100 milliseconds (ms) or more andapproximately 200 ms or smaller, for example. Due to this, the sum ofthe processing time of step S21 and the processing time of step S24 isapproximately 200 ms or more and approximately 400 ms or smaller, forexample.

In step S25 subsequent to step S24, the distance data processing unit 51calculates an external light distance on the basis of the reflectionrange-finding light (an external light) 37 received by the lightreceiving element 42. That is, the distance data processing unit 51processes an external light distance data on the basis of the reflectionrange-finding light 37 received by the light receiving element 42 andconverted to an electrical signal of the reflection range-finding light.Subsequently, in step S26, the distance data processing unit 51calculates the distance to the measurement target on the basis of theinternal light distance data and the external light distance data storedin the storage unit 48.

Subsequently, in step S27, the control operation unit 15 determineswhether one scanning operation has ended. When one scanning operationhas not ended (step S27: NO), the control operation unit 15 executes theabove-described process of step S25. That is, the control operation unit15 acquires the point cloud data for the entire measuring range or thepoint cloud data for the measurement target in the measurement of onescanning operation. For example, the control operation unit 15determines that one scanning operation has ended when a predeterminedperiod has elapsed from the start of measurement. Alternatively, forexample, the control operation unit 15 determines that one scanningoperation has ended when a change in temperature is a predeterminedvalue or more. That is, the control operation unit 15 determines thatone scanning operation has ended when an element which changes theinternal reference light 36 is present. In this manner, the end of onescanning operation is not limited to a fact that the scanning mirror 7makes one rotation about the vertical rotating shaft 6. The period inwhich the scanning mirror 7 makes one rotation about the verticalrotating shaft 6 is approximately 30 ms.

On the other hand, when one scanning operation has ended (step S27:YES), the control operation unit 15 determines whether the measurementhas ended in step S28. When the measurement has not ended (step S28:NO), the control operation unit 15 executes the above process of stepS21. That is, when an element that changes the internal reference light36 is present, the control operation unit 15 executes control so thatthe first shutter 53 is closed and the second shutter 54 is open (stepS21). The distance data processing unit 51 calculates the internal lightdistance on the basis of the internal reference light (an internallight) 36 received by the light receiving element 42 (step S22). Thatis, whenever one scanning operation ends, the distance data processingunit 51 processes (acquires) internal light distance data.

On the other hand, when measurement has ended (step S28: YES), thecontrol operation unit 15 ends the distance calculation process.

In this manner, the 3-dimensional measuring device 1A according to thiscomparative example performs control to open and close the first andsecond shutters 53 and 54. However, in the 3-dimensional measuringdevice 1A according to this comparative example, it is difficult toperform the switching operation of switching the first and secondshutters 53 and 54 at a high speed and it takes a considerable time inadjustment of an optical axis.

In contrast, in the 3-dimensional measuring device 1 according to thepresent embodiment, as described with reference to FIG. 3 , thereference light optical system 24 is provided in a range outside themeasuring range within the radiation range of the range-finding light 35and receives the range-finding light 35, reflected from the scanningmirror 7, as the internal reference light 36 and reflects the same.Therefore, in the 3-dimensional measuring device 1 according to thepresent embodiment, first, in step S11, the control operation unit 15controls the scanning mirror 7 to radiate the range-finding light 35 toa range outside the measuring range within the radiation range. That is,the control operation unit 15 controls the scanning mirror 7 to radiatethe range-finding light 35 to the reference light optical system 24 asthe internal reference light 36.

The internal reference light 36 having been received and reflected bythe reference light optical system 24 is reflected from the scanningmirror 7 and passes through the second beam splitter 39 and is guided tothe light receiving element 42. The distance data processing unit 51calculates the internal light distance on the basis of the internalreference light (an internal light) 36 received by the light receivingelement 42. That is, the distance data processing unit 51 processesinternal light distance data on the basis of the internal referencelight 36 received by the light receiving element 42 and converted to anelectrical signal of the internal reference light. Subsequently, in stepS12, the storage unit 48 stores the intrinsic optical distance data.

Subsequently, in step S13, the control operation unit 15 controls thescanning mirror 7 to radiate the range-finding light 35 to a measuringrange within the radiation range. That is, the control operation unit 15controls the scanning mirror 7 to radiate the range-finding light 35 tothe measurement target. The reflection range-finding light 37 reflectedfrom the measurement target present in the measuring range is reflectedfrom the scanning mirror 7 and passes through the second beam splitter39 and is guided to the range finding unit 22. The distance dataprocessing unit 51 calculates an external light distance on the basis ofthe reflection range-finding light (an external light) 37 received bythe light receiving element 42. That is, the distance data processingunit 51 processes external light distance data on the basis of thereflection range-finding light 37 received by the light receivingelement 42 and converted to an electrical signal of the reflectionrange-finding light.

Subsequently, in step S14, the distance data processing unit 51calculates the distance to the measurement target on the basis of theinternal light distance data and the external light distance data storedin the storage unit 48. Subsequently, the control operation unit 15determines whether the measurement has ended in step S15. When themeasurement has not ended (step S15: NO), the control operation unit 15executes the above process of step S11. That is, when the measurementhas not ended (step S15: NO), the control operation unit 15 controls thescanning mirror 7 to radiate the range-finding light 35 to the referencelight optical system 24 as the internal reference light 36 regardless ofwhether one scanning operation has ended (whether an element thatchanges the internal reference light 36 is present). That is, thedistance data processing unit 51 calculates the distance to themeasurement target (step S14), and when the measurement has not ended(step S15: NO), the distance data processing unit 51 processes(acquires) the internal light distance data whenever the distancecalculation ends.

In step S15 subsequent to step S14, when the measurement has ended (stepS15: YES), the control operation unit 15 ends the distance calculationprocess.

In this manner, in the 3-dimensional measuring device 1 according to thepresent embodiment, the control operation unit 15 does not controlopening and closing of the first and second shutters 53 and 54 wheneverone scanning operation ends. In the 3-dimensional measuring device 1according to the present embodiment, the distance data processing unit51 processes (acquires) internal light distance data whenever thedistance calculation ends. In this way, it is possible to eliminate ashutter's switching operation. Moreover, the light quantity of theinternal reference light 36 does not change depending on the radiationdirection (a scanning direction) of the range-finding light 35 but canbe changed by the reference light optical system 24. This is the same asthat described with reference to FIG. 3 . Due to this, it is possible toacquire internal reference lights 36 having different light quantitiesusing the reference light optical system 24 while suppressing aradiation range (a scanning range) of the range-finding light 35 foracquiring the internal reference light 36. In this way, it is possibleto suppress the measuring range from narrowing and to secure arelatively wide measuring range.

Next, a modification of the reference light optical system of thepresent embodiment will be described with reference to the drawings.When the constituent elements of a 3-dimensional measuring deviceaccording to a modification are similar to the constituent elements ofthe 3-dimensional measuring device according to the present embodimentdescribed with reference to FIGS. 1 to 3 , redundant description thereofwill be omitted appropriately, and the difference will be mainlydescribed.

FIG. 7 is a diagram illustrating a first modification of the referencelight optical system of the present embodiment. A reference lightoptical system 24A of this modification includes a density variablefilter 246, a reflecting sheet 244, and a filter 245. The reflectingsheet 244 and the filter 245 are the same as those described withreference to FIG. 3 . The density variable filter 246 is providedbetween the filter 245 and the reflecting sheet 244. The reference lightoptical system 24A of this modification is different from the referencelight optical system 24 described with reference to FIGS. 1 and 3 inthat the density variable filter 246 is provided rather than the motor241 and the density gradient filter 243.

The density variable filter 246 can change the optical density of aregion through which the internal reference light 36 passes. Due tothis, the transmittance of the internal reference light 36 with respectto the density variable filter 246 is variable. That is, the densitygradient filter 243 described with reference to FIG. 3 is one example ofthe density variable filter 246 of this modification. The configurationof the other main components is similar to that of the reference lightoptical system 24 described with reference to FIGS. 1 and 3 .

The internal reference light 36 having been reflected from the scanningmirror 7 and having passed through the filter 245 and the densityvariable filter 246 is reflected from the reflecting sheet 244. Theinternal reference light 36 reflected from the reflecting sheet 244passes through the density variable filter 246 and the filter 245 and isreflected from the scanning mirror 7. When the internal reference light36 passes through the density variable filter 246, the optical densityof a region in which the internal reference light 36 passes through thedensity variable filter 246 changes. That is, when the internalreference light 36 passes through the density variable filter 246, thetransmittance of the internal reference light 36 with respect to thedensity variable filter 246 changes. In this way, the internal referencelights 36 having different light quantities are guided to and acquiredby the scanning mirror 7. The internal reference light 36 reflected fromthe scanning mirror 7 passes through the second beam splitter 39 and isguided to the light receiving element 42.

According to this configuration, since the transmittance of the internalreference light 36 with respect to the density variable filter 246 isvariable, it is possible to acquire internal reference lights 36 havingdifferent light quantities using the reference light optical system 24Awhile suppressing a radiation range (a scanning range) of therange-finding light 35 for acquiring the internal reference light 36. Inthis way, it is possible to suppress the measuring range from narrowingand to secure a relatively wide measuring range.

The reference light optical system 24A of this modification may have atransmittance variable filter 247 instead of the density variable filter246. The transmittance variable filter 247 is provided between thefilter 245 and the reflecting sheet 244 and can change the transmittanceof the internal reference light 36. That is, the transmittance of theinternal reference light 36 with respect to the transmittance variablefilter 247 is variable. An example of the transmittance variable filter247 is a liquid crystal panel capable of changing a transmittanceaccording to a received electrical signal.

The internal reference light 36 having been reflected from the scanningmirror 7 and having passed through the filter 245 and the transmittancevariable filter 247 is reflected from the reflecting sheet 244. Theinternal reference light 36 reflected from the reflecting sheet 244passes through the transmittance variable filter 247 and the filter 245and is reflected from the scanning mirror 7. When the internal referencelight 36 passes through the transmittance variable filter 247, thetransmittance of the internal reference light 36 with respect to thetransmittance variable filter 247 changes. In this way, internalreference lights 36 having different light quantities are guided to andacquired by the scanning mirror 7. The internal reference light 36reflected from the scanning mirror 7 passes through the second beamsplitter 39 and is guided to the light receiving element 42.

According to this configuration, since the transmittance of the internalreference light 36 with respect to the transmittance variable filter 247is variable, it is possible to acquire internal reference lights 36having different light quantities using the reference light opticalsystem 24A while suppressing a radiation range (a scanning range) of therange-finding light 35 for acquiring the internal reference light 36. Inthis way, it is possible to suppress the measuring range from narrowingand to secure a relatively wide measuring range.

FIG. 8 is a diagram illustrating a second modification of the referencelight optical system of the present embodiment. A reference lightoptical system 24B of this modification includes a motor 241, areflectance gradient sheet 248, and a filter 245. The motor 241 and thefilter 245 are the same as those described with reference to FIG. 3 .The reference light optical system 24B of this modification is differentfrom the reference light optical system 24 described with reference toFIGS. 1 and 3 in that the reflectance gradient sheet 248 is providedrather than the density gradient filter 243 and the reflecting sheet244.

The reflectance gradient sheet 248 is supported by the shaft 242 of themotor 241 and is provided rotatable about the shaft 242 of the motor 241with the rotating force transmitted from the motor 241. A reflectance ofthe internal reference light 36 in the reflectance gradient sheet 248changes in the circumferential direction. In other words, a reflectancegradient in which the reflectance of the internal reference light 36changes in the circumferential direction is provided in the reflectancegradient sheet 248. The reflectance of the internal reference light 36in the reflectance gradient sheet 248 may not necessary increase ordecrease gradually in the circumferential direction but may change inthe circumferential direction.

When the reflectance gradient sheet 248 rotates with the rotating forcetransmitted from the motor 241, the reflectance of the internalreference light 36 reflected from the reflectance gradient sheet 248changes. That is, the internal reference light 36 having been reflectedfrom the scanning mirror 7 and having passed through the filter 245 isreflected from the reflectance gradient sheet 248. In this case, sincethe reflectance gradient sheet 248 is rotating, the reflectance of theinternal reference light 36 reflected from the reflectance gradientsheet 248 changes. In this way, internal reference lights 36 havingdifferent light quantities are guided to and acquired by the scanningmirror 7. The internal reference light 36 reflected from the scanningmirror 7 passes through the second beam splitter 39 and is guided to thelight receiving element 42.

According to this modification, when the reflectance gradient sheet 248rotates, the reflectance of the internal reference light 36 reflectedfrom the reflectance gradient sheet 248 changes. In this way, it ispossible to acquire internal reference lights 36 having different lightquantities while suppressing the radiation range (a scanning range) ofthe range-finding light 35 for acquiring the internal reference light36. In this way, it is possible to suppress the measuring range fromnarrowing and to secure a relatively wide measuring range.

Hereinabove, the embodiment of the present invention has been described.However, the present invention is not limited to the above-describedembodiment, and various changes can be made without departing from thescope of the claims. The components of the above-described embodimentmay be partially omitted or may be arbitrarily combined with each otherso as to be different from that described above.

What is claimed is:
 1. A 3-dimensional measuring device that radiates arange-finding light to a measurement target, measures a distance to themeasurement target on the basis of an internal reference light beam anda reflection range-finding light, which is the range-finding lightreflected from the measurement target, and detects a radiation directionof the range-finding light to thereby acquire 3-dimensional data on themeasurement target, the 3-dimensional measuring device comprising: alight source unit that emits the range-finding light; a projectionoptical system that radiates the range-finding light emitted from thelight source unit to a range-finding optical axis; a scanning mirrorthat is provided to be rotatable about a rotating shaft in a state ofbeing inclined with respect to a shaft center of the rotating shaft toradiate the range-finding light guided from the projection opticalsystem within a plane crossing the rotating shaft in a rotary manner; alight-receiving optical system that receives the reflectionrange-finding light having been reflected from the measurement targetand guided by the scanning mirror; a reference light optical system thatis provided in a range outside a measuring range, in which themeasurement target is irradiated with the range-finding light within aradiation range in which the range-finding light is radiated by thescanning mirror in a rotary manner, to receive and reflect therange-finding light, reflected from the scanning mirror, as the internalreference light, this reference light optical system being capable ofchanging a light quantity of the reflected internal reference light; anda light receiving element that receives the reflection range-findinglight and the internal reference light guided from the reference lightoptical system, wherein the reference light optical system includes: atransmittance variable filter capable of changing a transmittance of theinternal reference light according to a received electrical signal; anda reflecting sheet of retroreflection that reflects the internalreference light having passed through the transmittance variable filter.2. The 3-dimensional measuring device according to claim 1, wherein thetransmittance variable filter is a liquid crystal panel.